From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1753501AbbBZJ6r (ORCPT ); Thu, 26 Feb 2015 04:58:47 -0500 Received: from foss.arm.com ([217.140.101.70]:40482 "EHLO foss.arm.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1752706AbbBZJ6p (ORCPT ); Thu, 26 Feb 2015 04:58:45 -0500 Date: Thu, 26 Feb 2015 09:58:13 +0000 From: Catalin Marinas To: Huang Ying Cc: Linus Torvalds , LKML , LKP ML Subject: Re: [LKP] [futex] 76835b0ebf8: -8.1% will-it-scale.per_thread_ops Message-ID: <20150226095812.GA32538@localhost> References: <1424927813.10337.19.camel@intel.com> MIME-Version: 1.0 Content-Type: text/plain; charset=iso-8859-1 Content-Disposition: inline Content-Transfer-Encoding: 8bit In-Reply-To: <1424927813.10337.19.camel@intel.com> User-Agent: Mutt/1.5.21 (2010-09-15) Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Thu, Feb 26, 2015 at 05:16:53AM +0000, Huang Ying wrote: > FYI, we noticed the below changes on > > git://git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git master > commit 76835b0ebf8a7fe85beb03c75121419a7dec52f0 ("futex: Ensure get_futex_key_refs() always implies a barrier") > > > testbox/testcase/testparams: lkp-wsx01/will-it-scale/performance-futex4 > > 0429fbc0bdc297d6 76835b0ebf8a7fe85beb03c751 > ---------------- -------------------------- > %stddev %change %stddev > \ | \ > 6314259 ± 0% -8.1% 5800079 ± 0% will-it-scale.per_thread_ops > 6274871 ± 0% -8.1% 5768747 ± 0% will-it-scale.per_process_ops This was raised before but I'm not sure we can do much about it: https://lkml.org/lkml/2014/10/26/189 It would be interesting to know the difference in performance with the code prior to commits b0c29f79ecea and 11d4616bd07f which optimised the futex code but missed a barrier. -- Catalin